Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology that allows a health care provider to visualize internal structures of the body. An MRI device closely surrounds the patient and includes a superconducting magnet that requires a cooling system. In this regard, a compressor transfers a cooling medium, such as helium or nitrogen, through a supply conduit to a heat exchanger that transfers heat from the magnet to the cooling medium. The cooling medium is then transferred through a return conduit back to the compressor.
The MRI equipment and cooling system generates noise and vibration. The flow of cooling medium through the heat exchanger creates noise and vibration that can be increased by the conduits connected to the heat exchanger that function as an amplifier. Still further, the flow of cooling medium through the conduits themselves generates noise and vibration should the inner surfaces of the conduits have irregularities or otherwise be unsmooth.
One example of a cold head that may be incorporated into an MRI is disclosed with reference to U.S. Pat. No. 5,361,588 to Asami, the contents of which are incorporated by reference herein in their entirety for all purposes. Noise and vibration from the heat exchanger and/or conduits may disturb the patient and make him or her apprehensive, especially considering the fact that the patient is in close proximity to the MRI equipment and potentially already on edge. If the patient is uncomfortable or apprehensive during an MRI procedure he or she may move and ruin the measured reading which requires the patient to remain still. Therefore, aside from being only an annoyance, noise and vibration generated in the cooling of MRI equipment functions to increase the cost of operating the equipment and the time in obtaining results.
In order to reduce noise and vibration associated with MRI cooling, United States Patent Publication No. 2008/0134692 to Crowley discloses a conduit for the transfer of cooling medium includes an inner conduit surrounded by and coaxial with an outer conduit. Input cooling medium flows through the inner conduit and output, warmed cooling medium flows back through the outer conduit. The opposite direction of flow of this gas within the conduits is stated as having a canceling effect to reduce noise in the cooling process. United States Patent Publication No. 2008/0134692 is incorporated by reference herein in its entirety for all purposes.
Another design implemented for the transfer of cooling medium in cryopump-type systems disclosed in U.S. Pat. No. 6,094,922 to Ziegler employs a smooth bore input tube that is separated from a smooth bore output tube. The two tubes are surrounded by an umbilical cord and a vacuum is created in the space within the umbilical cord. Although capable of managing heat transfer in the system, such a design does not reduce noise generated by the cooling system. This design involves the transfer of a liquid cooling medium and not a gas cooling medium. U.S. Pat. No. 6,094,922 is incorporated by reference herein in its entirety for all purposes. Although various designs of cooling systems exist, there remains room for variation and improvement in the art.